# US 2008/0185982 A1 · Cylinder-Type Linear Motor and Moving Part Thereof > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2008/0185982 A1 - Document ID: US20080185982A1 - Status: Published application - Kind: A1 - Application number: 12/098,148 - Filed: 2008-04-04 - Published: 2008-08-07 - Earliest claimed: 2004-08-09 - Assignees: Oriental Motor Co., Ltd. - Inventors: Takao Iwasa; Hirobumi Satomi - Web page: https://patentgrep.com/patent/US20080185982A1 ## CPC - H02K 41/03: Synchronous motors; Motors moving step by step; Reluctance motors (H02K41/035 takes precedence) - H02K 33/00: Motors with reciprocating, oscillating or vibrating magnet, armature or coil system (arrangements for handling mechanical energy structurally associated with motors H02K7/00, e.g. H02K7/06) - H02K: DYNAMO-ELECTRIC MACHINES (dynamo-electric relays H01H53/00; conversion of DC or AC input power into surge output power {H03K3/53}) ## Abstract There is provided a cylinder-type linear motor capable of shortening the total motor length with respect to a predetermined stroke length S and capable of being operated without sensor means for sensing the position of a moving part being added in the axial direction. The cylinder-type linear motor includes a fixed part 20 having a coil assembly 28 formed by a plurality of (n number of) ring-shaped coils 22 . . . 27 arranged in the axial direction and a yoke member 21 made of a magnetic material, and a moving part 10 having a linear motion shaft 11 provided on the axis line of the fixed part 20 and a permanent magnet assembly 15 having one or more permanent magnets magnetized in the axial direction. A stroke S is equal to or smaller than (n×C−M), the axial length Y of the yoke member is set equal to or larger than (M+S+0.8×D), and the ring-shaped coils 22 . . . 27 are arranged in a predetermined phase order and the ring-shaped coils of the same phase are connected to each other to form one phase winding. Also, there is provided a moving part of a cylinder-type linear motor, which can improve the magnetic flux density distribution waveform near both end portions of the moving part assembly and can improve the thrust characteristic by bringing the magnetic flux density distribution waveform closer to a cosine waveform and by increasing the amplitude of cosine waveform. In this moving part, a permanent magnet assembly 5 has a pair of permanent magnets 2 and 4 magnetized in the axial direction, which are arranged so that the end faces with the same polarity face to each other; a pair of ring-shaped fixing members 6 and 7 each having an outside diameter smaller than the outside diameters of the paired permanent magnets 2 and 4, which are fixed on the linear motion shaft 11 so as to be in contact with both sides of the paired permanent magnets 2 and 4; and a pair of ring-shaped permanent magnets 8 and 9 magnetized in the radial direction so that the polarity on the outer peripheral surface is different from the polarity on the opposed end faces of the paired permanent magnets 2 and 4, which are provided on the outer peripheral surfaces of the paired ring-shaped fixing members 6 and 7. ## Claims ### Claim 1 A cylinder-type linear motor comprising: a fixed part including a coil assembly having a plurality of (n number of) ring-shaped coils disposed in the axial direction with an equal pitch to form a cylindrical space, and a yoke member made of a magnetic material, which is provided on the outer periphery side of the coil assembly; and a moving part including a linear motion shaft provided on the axis line of the fixed part so as to be capable of reciprocating in the axial direction, and a permanent magnet assembly having one or more permanent magnets magnetized in the axial direction, which is provided on the linear motion shaft, characterized in that when the pitch of the ring-shaped coil is taken as C, the axial length of the permanent magnet assembly as M, and the outside diameter thereof as D, a stroke S is equal to or smaller than (n×C−M), the axial length Y of the yoke member is set equal to or larger than (M+S+0.8×D), and the ring-shaped coils are arranged in a predetermined phase order and the ring-shaped coils of the same phase are connected to each other to form one phase winding. ### Claim 2 (depends on 1) The cylinder-type linear motor of claim 1, characterized in that the permanent magnet assembly of the moving part is arranged so that when the number of permanent magnets is two or more, the polarities of adjacent magnets facing each other is the same. ### Claim 3 (depends on 1) The cylinder-type linear motor of claim 1, characterized in that the yoke member is formed by a cylindrical member, an opening extending in the axial direction is provided in the cylindrical member, and sensor means for sensing the magnetic pole position of the moving part is provided in the opening. ### Claim 4 (depends on 1) The cylinder-type linear motor of claim 1, characterized by being driven by a driving circuit having sensor means for sensing the magnetic pole position of the moving part, which is provided in the outer peripheral surface of the coil assembly; a moving part magnetic pole position detecting section for detecting the magnetic pole position of the moving part by means of a signal from the sensor means; a memory section for storing pattern data that are set so as to correspond to the moving part magnetic pole position and to correct asymmetry of magnetic flux density distribution waveform caused by the configuration of the permanent magnet assembly and asymmetry of mating winding existing in the case where the number of ring-shaped coils is different according to the phase; a current control section in which a current command value of each phase is produced based on the pattern data read from the memory section so as to correspond to the moving part magnetic pole position and a current command from a speed control section, the current command value is compared with an actual current value sent from a current detecting section for detecting a current flowing in each phase winding, and a gate signal for carrying out PWM control is generated so that the difference is zero; and an inverter section provided with switching means that is ON/OFF controlled by the gate signal from the current control section.